With the advent of static electronic stitch pattern data circa 1974, sewing machines so equipped have routinely included DC power supply arrangements connected to the regular AC house mains. Since the cost and other disadvantages of such AC connected power supplies, such as disclosed for instance in U.S. Pat. No. 3,984,745, Oct. 5, 1976 of Minalga, are essential to and justified by the advantages of the electronic memory, such power supplies are available in electronic memory sewing machines also to supply other sensing and indicating devices; and indeed, numerous electronic sensing and indicating devices have been developed for use in electronically controlled sewing machines equipped with AC connected power supplies. One example of such a sensing and indicating device is a low bobbin thread detecting system as disclosed in U.S. Pat. No. 4,413,581, Nov. 8, 1983 of Logan which is incorporated herein by reference.
While is may be advantageous to incorporate or retrofit such a low bobbin thread detection system or other similar electronic sensing and indicating device in a sewing machine without electronic memory such as a cam controlled ornamental stitcher or a straight stitch sewing machine, the cost and disadvantage of an AC connected power supply has made such adaptation impractical.